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mid-15c., a back-formation from prodigality, or else from Middle French prodigal and directly from Late Latin prodigalis, from Latin prodigus "wasteful," from prodigere "drive away, waste," from pro- "forth" (see pro-) + agere "to drive" (see act (v.)). First reference is to prodigial son, from Vulgate Latin filius prodigus (Luke xv:11-32). As a noun, "prodigal person," 1590s, from the adjective (the Latin adjective also was used as a noun).